1. Field of the Invention
The present invention relates to a process for preparing a carbon monoxide conversion catalyst that converts carbon monoxide contained in a gas such as air into carbon dioxide highly efficiently even at room temperature.
2. Description of the Prior Art
Among catalysts to convert carbon monoxide into carbon dioxide is platinum supported on activated carbon. (See, for example, Japanese Patent Publication No. 36014/1982.) This CO conversion catalyst is produced by treating activated carbon of proper grain size, which has been washed with hydrochloric acid and dried in optional pretreatment, with an aqueous solution of chloroplatinic acid (H.sub.2 PtCl.sub.6), followed by drying, reducing the chloroplatinic acid with an aqueous solution of KBH.sub.4 or the like, followed by rinsing and drying, and finally heating the treated activated carbon at a high temperature in the air. The CO conversion catalyst produced by the conventional process like this is not satisfactory in CO conversion efficiency. Moreover, it sharply decreases in CO conversion efficiency as the flow rate of CO-containing gas increases. There is an instance, for example, where the CO concentration at the exit increases from 20 ppm to 170 ppm as the space velocity increases from 5,300 hr.sup.-1 to 10,600 hr.sup.-1.
Another disadvantage of the conventional CO conversion catalyst produced by the above-mentioned process is that it loses its initial catalytic performance to a great extent after it has been left under humid conditions for a long period and its recovery takes a very long time.